1. Field of the Invention
The present invention relates to a method for safely reacting active metals. In another aspect, the present invention relates to a method for safely converting active metals into metal hydroxides. In still another aspect, the present invention relates to a method for the insitu conversion of active metals into metal hydroxides.
2. Description of the Related Art
Active metals such as sodium, potassium, lithium, and calcium are widely used because of their valuable properties.
Both potassium and sodium have been used in commercial processes for the production of aluminum as reducing agents, and both have been utilized as heat transfer medium in chemical or nuclear reactors and other applications.
Potassium is also used in the production of potassium superoxide for life support systems. Potassium also enhances the activity of some catalysts, and has some application in magnetohydrodynamics.
The production of tetraethyllead and tetramethyllead and other antiknock agents for gasoline is one of the largest outlets for sodium. Refractory metals such as titanium, zirconium, and hafnium are manufactured by sodium reduction of their halides. Sodium is employed as a reducing agent in numerous other processes, including the preparation of dyes, herbicides, pharmaceuticals, high molecular weight alcohols, perfume materials, and isosebacic acid. Sodium can even function as a catalyst for many polymerizations, such as the polymerization of 1,2-butadiene (the Buna process) and the copolymerization of styrene-butadiene mixtures (the modified GRS process).
Lithium is also utilized as a component of reducing systems for organic compounds. Lithium has been proposed as a breeding blanket and reactor coolant in magnetic fusion energy facilities.
The widescale industrial use of metals, such as potassium, lithium, sodium and calcium has created the need to dispose of waste containing such metals, and the need to clean equipment or articles of manufacture. Even the transportation of such metals can create problems. For example, in the transportation of sodium, it is poured in liquid form into a railway tankcar. Upon reaching the desired destination the sodium is liquified and drained out of the tankcar, by passing hot oil through a Jacket or coils around the tankcar. Unfortunately, the draining is never complete as some sodium residue is left in the tankcar and builds with each draining. After several such drainings the residue, referred to as a "sodium heel" or "sludge" may build up to and even exceed about 15,000 pounds for a tankcar with an approximate 100,000 pound sodium capacity.
Cleaning, however, is difficult as these metals are quite hazardous because of their high chemical reactivity with water and the danger of explosive reactions. These metals react readily with ambient atmospheric moisture to liberate hydrogen gas and much heat. The reaction of sodium, for example, is sufficiently exothermic to result in ignition or explosion of the hydrogen gas and ignition of the sodium metal. The current state of the art method of cleaning reactive metals from tankcars, tanks and storage containers is to first purge with dry air, and then to manually remove the reactive metal, and then to ship it off to be incinerated. However, this method is very labor intensive and is potentially quite hazardous.
Numerous other prior art methods to dispose of active metals and to clean equipment or articles of manufacture have been proposed.
Such prior art methods include the method of introducing sodium sludge into the lower portion of an upflowing stream of an aqueous sodium hydroxide solution and a method of reacting alkali metals by providing a pool of liquid metal hydroxide within a confined area, introducing an alkali metal feed above the upper surface of the pool, and passing steam through the pool to contact the alkali metal at its surface.
Other disposal methods for alkali metals include ocean dumping which relies on the vast quantities of water to dilute the caustic so formed and the ocean air to quickly dilute the hydrogen concentration to a safe level or forcing molten alkali metal through a nozzle underwater at sufficient velocity to cause the alkali metal to break up into a fine spray which will react instantly with the water.
Alkali metals have also been reacted in a two-layer liquid system with the top layer being a nonreactive liquid and the bottom layer being a reactive liquid, reacted by being sprayed into a disposal solution, or reacted by being sprayed by a solution while floating in metal hydroxide.
Complex multi-step reaction methods have also been proposed comprising dissolving an alkali metal into an inert metal, contacting the melt with a salt containing the alkali metal hydroxide and a gas containing oxygen, which converts the alkali metal to an oxide which is dissolved in the salt. The salt is separated from the melt and contacted with a gas containing water to convert the alkali metal oxide to its hydroxide.
It is even known that equipment may be cleaned by being opened to air and heated until any sodium present is oxidized, or by purging thoroughly with nitrogen, then slowly admitting dry steam to the system while maintaining the nitrogen purge.
However, many of the prior art methods implicity require that the reactive metal first be removed prior to reacting it to a less reactive state or are only practical for lesser amounts of reactive metal than for example, the thousands of pounds of sodium heel that is typically found in a railcar or other containers.